The disclosed subject matter relates generally to the treatment of end stage renal failure and more specifically to devices, methods, systems, improvements, and components for performing peritoneal dialysis.
Peritoneal dialysis is a mature technology that has been in use for many years. It is one of two common forms of dialysis, the other being hemodialysis, which uses an artificial membrane to directly cleanse the blood of a renal patient. Peritoneal dialysis employs the natural membrane of the peritoneum to permit the removal of excess water and toxins from the blood.
In peritoneal dialysis, sterile peritoneal solution is infused into a patient's peritoneal cavity using a catheter that has been inserted through the abdominal wall. The solution remains in the peritoneal cavity for a dwell period. Osmosis exchange with the patient's blood occurs across the peritoneal membrane, removing urea and other toxins and excess water from the blood. Ions that need to be regulated are also exchanged across the membrane. The removal of excess water results in a higher volume of fluid being removed from the patient than is infused. The net excess is called ultrafiltrate, and the process of removal is called ultrafiltration. After the dwell time, the dialysate is removed from the body cavity through the catheter.
Peritoneal dialysis requires the maintenance of strict sterility because of the high risk of peritoneal infection. The risk of infection is particularly high due to the long periods of time that the patient is exposed to the dialysate.
In one form of peritoneal dialysis, an automated cycler is used to infuse and drain dialysate. This form of treatment can be done automatically at night while the patient sleeps. One of the safety mechanisms for such a treatment is the monitoring by the cycler of the quantity of ultrafiltrate. The cycler performs this monitoring function by measuring the amount of fluid infused and the amount removed to compute the net fluid removal.
The treatment sequence usually begins with an initial drain cycle to empty the peritoneal cavity of spent dialysate, except on so-called “dry days” when the patient begins automated treatment without a peritoneum filled with dialysate. The cycler then performs a series of fill, dwell, and drain cycles, typically finishing with a fill cycle.
The fill cycle presents a risk of over-pressurizing the peritoneal cavity, which has a low tolerance for excess pressure. In traditional peritoneal dialysis, a dialysate container is elevated to certain level above the patient's abdomen so that the fill pressure is determined by the height difference. Automated systems sometimes employ pumps that cannot generate a pressure beyond a certain level, but this system is not foolproof since a fluid column height can arise due to a patient-cycler level difference and cause an overpressure. A reverse height difference can also introduce an error in the fluid balance calculation because of incomplete draining.
Modern cyclers may fill by regulating fill volume during each cycle. The volume may be entered into a controller based on a prescription. The prescription, which also determines the composition of the dialysate, may be based upon the patient's size, weight, and other criteria. Due to errors, prescriptions may be incorrect or imperfectly implemented resulting in a detriment to patient well-being and health.
Systems that measure pressure have been proposed. For example, a pressure sensor in contact with a fluid circuit at the cycler has been described. The sensor indicates the pressure at the proximal end of the fill/drain line. During operation, a controller connected to the pressure sensor changes the operation of the peritoneal dialysis machine in response to changes in pressure sensed by the pressure sensor.